1. Field
Exemplary embodiments of the present invention relate to a nonvolatile memory device and a method for fabricating the same.
2. Description of the Related Art
A nonvolatile memory device is a memory device capable of storing data even though power supply is off. Various nonvolatile memory devices, for example, a NAND type flash memory, are widely used.
FIG. 1 is a cross-sectional view illustrating a conventional nonvolatile memory device.
Referring to FIG. 1, a substrate 10 with active regions 10A, which are defined by an isolation layer 11, is provided.
A tunnel dielectric layer 12 and floating gates 13 are disposed on the active regions 10A. The tunnel dielectric layer 12 and the floating gates 13 are formed in a stack structure over the respective active regions 10A when viewed in the transverse direction of the cross-section.
An intergate dielectric layer 14 is disposed on the resultant structure including the tunnel dielectric layer 12 and the floating gates 13. The intergate dielectric layer 14 is formed along the underlying profile.
Control gates 15 are disposed on the intergate dielectric layer 14 to extend in the transverse direction of the cross-section.
In the nonvolatile memory device configured as mentioned above, a program operation for storing charges in the floating gates 13 or an erase operation for removing the charges stored in the floating gates 13 is performed according to a voltage applied to the control gates 15.
As a semiconductor device is highly integrated, the width of the floating gates 13 or the gap between the floating gates 13 markedly decreases. Because the channel length L of a memory cell decreases as the width of the floating gates 13 decreases, leakage current increases, and securing a threshold voltage of a desired level is difficult upon performing the program operation. Also, as the gap between the floating gates 13 decreases, spaces for forming the control gates 15 become insufficient when the intergate dielectric layer 14 is formed between the floating gates 13 (see the reference symbol A).